1. Field of the Invention
The present invention relates to a conveyor chain for loading and conveying articles and more specifically to a conveyor chain for loading and conveying the articles by magnetically attracting and retaining them even when a conveying surface is sloped or slippery.
2. Related Art
One example of a conveyor chain that is currently used in the art is the conveyor belt 500 shown in FIG. 11. The conveyor belt 500 has link rows each having a predetermined chain width W and composed of link modules 510. The link modules 510 include a loading portion 511 for loading articles M (referred to simply as ‘conveyed articles’ or as ‘articles’ hereinafter) and hinge portions 512 projecting respectively from front and rear parts of the loading portion 511. A single link module 510 extends across a chain width direction. The conveyor belt 500 is constructed by linking a large number of link modules 510 in a predetermined array pattern in a chain longitudinal direction by inserting link pins 520 into pin inserting holes 513 formed in the hinge portions 512. Then, the conveyor belt 500 is suspended around driving and driven sprockets S1 and S2 to convey the articles M such as drink bottles, drink cans and the like as disclosed in Japanese Patent Application Laid-open No. 2004-262600 (Col. 6, FIG. 1).
In another conveyor chain currently known in the art, there is a magnet-equipped chain comprising a large number of attracting magnetic units each of which is constructed by coating a surface of a permanent magnet bonded to a thin ferromagnetic yoke by epoxy resin or the like. The magnetic units are disposed on an outer peripheral side of a chain base portion at predetermined intervals to convey magnetically attractive articles by attracting and retaining such articles as is disclosed in Japanese Patent Application Laid-open No. Hei. 9-275011 (Page 8, FIG. 8).
In still another conveyor chain known in the art, a magnetic chain conveyor for conveying cases formed of a magnetic material such as a drink box made of iron is used which has magnets mounted to yokes on both sides in a chain longitudinal direction as disclosed in Japanese Patent Application Laid-open No. Hei. 8-310384 (Col. 3, FIG. 10 (see Patent Document 3 for example).
One problem with each of the conveyer chain shown in FIG. 11, however, is that because the link module 510 for loading the articles M on the loading portion 511 is molded of synthetic resin to exhibit a self-lubricant properties, there is a problem in that it is unable to steadily convey the articles M because they may suddenly fall or slip when a shock is made a conveyor surface or when a component force in a slope direction acting on the articles M exceeds a frictional force of conveying the articles M on a slope, as shown in FIG. 12. Additionally, when a slippery liquid such as soapy water, lubricant oil or others spreads on the link module 510 and the loading surface of the loading portion 511 for loading the articles M of the link module 510 is excessively slippery, there may be other difficulties.
The prior art magnet-equipped chain also problems. That is, a large number of attracting magnetic units are disposed on the outer peripheral surface of the chain base portion which project on both right and left sides of the chain base portion. This means that the chain width must be increased in order to make room for the attracting magnetic units projecting on the right and left side of the chain base portion. The chain also causes such problems for device design that it hinders in dimensioning layouts of a chain guide, driving sprocket and others and that a chain turning radius increases excessively in conveying while turning horizontally.
If the chain base portion is narrowed along with the projecting parts of the attracting magnetic units to solve the abovementioned problems, there arises another problem that chain strength is remarkably weakened.
Still more, because the attracting magnetic units are disposed on the outer peripheral surface of the chain base portion, a radius of bending in a direction opposite from the conveyor surface, i.e., so-called ‘back-bend radius’, becomes large. As a result, it becomes unable to fully assure a slack even if an intermediate roller such as an idle roller is used to absorb elongation of the chain return side. Then, there are such problems that a frequency of burdens of maintenance for eliminating the elongation of the chain increases and if the chain is left as it is, the magnet-equipped chain bites into the driving sprocket and is cut.
Still more, because the prior art magnet-equipped chain is constructed by melting epoxy resin and the like at high temperature and coating it on the surface of the permanent magnet bonded to the ferromagnetic yokes, the permanent magnet is exposed to the high resin temperature. Then, the permanent magnet decreases its magnetism and cannot exhibit a sufficient attracting and retaining force. Furthermore, because the attracting magnetic unit is constructed by bonding the permanent magnet to the ferromagnetic yoke by an adhesive, the adhesion between the permanent magnet and the ferromagnetic yoke may wear off when used for a long period of time. Then, there are such problems that the permanent magnet may fall out and be damaged and it is unable to stably attract and retain the articles to be conveyed.
Still more, because the magnets in the prior art magnetic chain conveyor are attached to the yokes on the both sides, there are such problems that the magnets may suddenly fall out or are damaged by receiving a shock and others during conveyance and it may become unable to stably convey the articles. Then, it may also cause a problem that broken pieces of the magnets scatter around the conveying area, causing much trouble in terms of the conveyance works.